Fahmy 3030 A&P Exam

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Classes of Neurotransmitters..

Ach Biogenic Amines- Emotion and biological clock Amino Acids and Derivatives-All function in CNS

Local potentials can produce...

Action Potential

Costitiutively Open

Also called Leak Channels Responsible for resting membrane potential

Cholinergic Receptors

Always excitatory

CNS Damage Causes:

Alzheimers Stroke Epilepsy

Polarization of membrane

Any state + or - other than 0mV Unequal separation of charges

Interneurons

Are only found in CNS Lie between A+E neurons Form associations

Types of Neuroglia

Astrocytes Microglia Ependymal Oligodendrocytes (CNS) Schwann Cells (PNS)

Multiple Sclerosis

Axons lose myelin Slow transmission of impulse

Divergence

Branching Axon terminals affect thousands of postsynaptic cells

Electrical changes occur by changes in ion permeability

By Stimuli Change in charge across membrane Interaction of chemical messenger and receptor Changes in leak/pump cycle

Regeneration of Nerve Fibers

CNS- Cant regenerate PNS- Regenerate lost functions

Antagonists

Can be used to block the activity of agonists

Two Neurons

Can interact at same synapse

EPSP and IPSP can...

Cancel eachother out

Direct Acting Neurotransmitters

Cause an immediate change in membrane potential

Effecting Neural Function

Change in pH of ECF or blood Changes in ion composition of ECF Changes in body temp.

Thermally Gated

Channel changes open at specific temperatures

Voltage Gated

Channel changes open depending on membrane voltage

Ligand (chemical)- Gated Channel

Channel changes open probability depending on whether neurotransmitter or other chemical is bound

Mechanically Gated

Channel changes open when cell surface is deformed

Ganglion

Cluster of cell bodies in PNS

Nerve

Clusters in PNS

White matter

Composed of bundles of myelinated axons

Fluids are...

Conductors (low resistance)

Contiguous Conduction

Continues down length of axon

Epilepsy

Could be caused by defect in myelination

Synapses have...

Delays in info transfer

Extensions of Neuron

Dendrites Axon

General Senses

Detected from Integument

Summation of Presynaptic Inputs

Determine if action potential will occurs Sum of it all is called Grand Postsynaptic Potential (GPSP)

Explosive depolarization occurs...

Due to opening of Na+ channels by positive feedback

Excitatory Postsynaptic Potentials

EPSP Depolarize postsynaptic neuron Na+ diffuses into cell

Neuron Properties...

Excitability Conductivity Secretion of neurotransmitters

Nerve and muscle tissues are _________________

Excitable Can undergo rapid change in membrane potential

Adrenergic Receptors

Excitatory or inhibitory

Astrocytes

Form blood brain barrier Only allow Glucose most lipids and fat soluble molecules Alcohol Protect neurons Form Scar tissue after injury

Oligodendrocytes

Form myelin sheaths around axons in the CNS

Tay-Sachs

Gangliosides build up in nervous tissue

The Na+/K+ ATPase pump

Gradually restores the concentration of gradients disrupted by action potentials

ALL cells possess a ______________________

Membrane potential Seperation of charges across membrane

Repolarization

Membrane returns to resting potential after depolarization Ex: 0mV to -70mV

At rest potential=

Most channels closed

Retrograde Transport

Move mitochondria vesicles towards cell body

Voltage changes caused by...

Movement of ions across the cell membrane via special ion channels

Fast Anterograde Transport

Movement of mitochondria vesicles away from cell body

Anaxomic Neurons

Multiple dendrites No axon Communicate but do not produce electricity In brain Astrocytes

Action Potential Trigger

Must depolarize membrane threshold around -50mV

Cytosol Concentration

Negative

Neurons support cells

Neuroglia

PNS Damage Cause:

Neuropathy MS

Synapse of Neuron

Neurotransmitters

Neuroglia Functions

Nourish, Protect, and insulate neurons

Exogenous Neurotoxins

Obtained from environment Gases Metal

Saltatory Conduction

Occurs in myelinated fibers Skip from one node to next

Microglia

Odd microphages are phagocytosis

Bipolar Neurons

One axon One dendrite Common in special sense organs (eye and ear)

Multipolar Neurons

One axon 2 or more dendrites Most common as somatic or motor neurons

Local Potentials Die Out..

Over short distances

Dopamine too long in synapse

Overstimulation of pleasure pathways Drug required for pleasure Physiological addiction

Peptides

Pain mediators Act indirectly through secondary messengers

Neurotransmitter Disorders

Parkinsons Myasthenia Gravis Mental Illness

Local Potentials spread by..

Passive Flow

Venom

Plug ion channel pores Increase Na+ permeability causing cells to be unable to send Action Potential

Extracellular Fluid

Positive

Endogenous Neurotoxins

Produced by body Glutamate Excitotoxicity

Slow Anterograde Transport

Proteins

Nerve/Muscle tissue can change resting potentials into electrical signals by...

Rapidly changing the polarity and permeability of the membrane

Graded/Local potentials

Receptor, pacemaker... Repolarize quickly

Tract

Region of white matter Axons in CNS

Local Anesthetics

Reversibly bind voltage-gated Na+ channels Prevent the formation of action potentials

Relative Refractory Period

Time when K+ channels still open slow to close

Absolute Refractory Period

Time when action potential is occuring

Gray matter

Unmyelinated axons

Electrochemical gradients

Used to maintain transmembrane potential

Length of Refractory Period...

Varies among cell types

E (equilibrium)=

-70mv

How neurons convert and transmit information

1. Energy is converted to an electrical signal which will translate to a chemical signal in a presynaptic neuron 2. Chemical interacts with postsynaptic cell which converts chemical signal back to electrical signal in postsynaptic neuron

Converging Input

A single cell is influenced by thousands of presynaptic cells

Triggering events are received by...

A soma of neuron or dendrites

Purines

ATP

Inhibitory Postsynaptic Potentails

IPSP Hyperpolarize the postsynaptic neuron K+ goes out and/or Cl- diffuses into cell

Guillain Barre Syndrome

Inflammation causing loss of myelin in Peripheral nerves and spinal roots

Lipids/Plasma membrane..

Insulators (high resistance)

How is membrane potential established/maintained

K+ is dominant Na+/K+ ATPase maintains concentration differences

Action Potentials

Large changes in electrochemical gradients Travel long distance All or none

Ependymal Cells

Line ventricles and central canal Produces and Maintains CSF

Nerve Fiber

Long fiber or process = Axon

Schwann Cells

Make myelin sheaths

Hyperpolarization

Makes membrane more polarized More negative inside Ex: -70mV to -80mV

Depolarization

Makes the membrane potential less negative than resting potential towards 0mV Ex: -70mV to -20mV

Myelin Sheath Not Fully Formed

May cause epilepsy

How is membrane potential established?

Membrane itself is not charged, however the fluid on either side is charged

Efferent Neuron

Sends a motor signal away from CNS to an effector organ Long peripheral axon in PNS Usually in brain except reflex

Afferent Neuron

Sends signals toward the CNS Generates action potentials from sensory receptors Long axon found in PNS

Membrane Potential

Seperation of charges across a membrane

Cell Body Contains...

Soma Nucleus & nucleolus Neurofibrils Nissl bodies Axon Hillock No Centrioles

Pseudo-Unipolar neurons

Soma to the side Axon and dendrite are continuous Afferent fibers from sensory receptors

Sattelite Cells

Surround somas or ganglion

Dissolved Gases

Synthesized when needed Not stored in vesicles


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